An apparatus 10Z shown in FIG. 1 is a press forming apparatus configured to press-forming a body of an automobile. The apparatus 10Z includes the followings.                A base 11.        A fixed die 12. It is fixed to the base 11.        A pivoting body 14. It is configured to pivot around a shaft 41 parallel to an L-R direction, shown in FIG. 2.        A cylinder 13. It is configured to move a piston 31 toward an F-B direction. This produces pivot movement of the pivoting body 14, via transmission block 42.        A movable die, not shown. It is configured to move toward a U-D direction, and to press a workpiece 20 placed on the fixed die 12. The workpiece 20 is sandwiched and processed between the movable die and the fixed die 12 and a forming portion 43 of the pivoting body 14.        
Pivot movement of the pivoting body 14 enables to process the workpiece 20 into a shape having negative angles. This reduces the number of steps to produce bodies of automobiles, such as front fenders or hood outer panels, or other products having complex shapes.
An apparatus produced and sold as “Swing Die™” by Yourbusiness Co., Ltd. of Tokyo, Japan is known as the above described press forming apparatus.
As shown in FIGS. 2 and 3, the apparatus 10Z includes bearing units 15Y and 15Z. The bearing units 15Y and 15Z are configured to support the shaft 41 of the pivoting body 14 with capacity of pivot movement. The bearing unit 15Z has an upper block 56Z and a lower block 58Z. The bearing unit 15Y has a mirror image shape of the bearing unit 15Z, and has an upper block 56Y and a lower block 58Y.
The lower blocks 58Y and 58Z are fixed to the base 11 by using fixing members such as bolts. When the apparatus 10Z is assembled, the shaft 41 of the pivoting body 14 is mounted on the lower blocks 58Y and 58Z. Then, the upper blocks 56Y and 56Z are mounted on the lower blocks 58Y and 58Z on which the shaft 41 is mounted, and fixed by using fixing members such as bolts.
The pivoting body 14 is very heavy, and pulled up with a crane or the like to move it. This makes it extremely difficult to insert the shaft 41 into a shaft hole portion of the bearing unit from the side. Dividing of the bearing units 15Y and 15Z into upper and lower parts makes it easy to assemble the apparatus 10Z.
As shown in FIG. 4, a recess 61Z, or upper recess, with a semicircular column shape, shown in FIG. 8, is provided on a lower face, or a D side face, of the upper block 56Z. An upper bush 57 is fixed in it. A recess 81, or lower recess, with a semicircular column shape, shown in FIGS. 11 and 12, is provided on a upper face, or a U side face, of the lower block 58Z. A lower bush 59 is fixed in it. In this manner, the shaft hole portion of the bearing unit 15Z is formed by combining the recess 61Z of the upper block 56Z and the recess 81 of the lower block 58Z.
As shown in FIGS. 5 and 6, the upper bush 57 has a semi-cylindrical shape, is made of cast iron or the like, and has a countersink 71. The countersink 71 penetrates the upper bush 57 near the center of it. A flat head bolt 51a, shown in FIG. 14, is inserted through it. The flat head bolt 51a fixes the upper bush 57 to the upper block 56Z.
As shown in FIGS. 7 and 8, the upper block 56Z is made of steel or the like, and includes the followings.                A female screw hole 66. It is bored near the center of the recess 61Z toward a U direction. It engages with the flat head bolt 51a to fix the upper bush 57 to the upper block 56Z.        Positioning holes 64a and 64b. They penetrate the upper block 56Z in the U-D direction. Knock pins 55a and 55b, shown in FIG. 13, are fitted through them. The knock pins 55a and 55b fix the positional relation between the upper block 56Z and the lower block 58Z.        Bolt holes 62a to 62c. They penetrate the upper block 56Z in the U-D direction. Bolts 53a to 53c, shown in FIG. 13, are inserted through them. The bolts 53a to 53c fix the upper block 56Z to the lower block 58Z.        
As shown in FIGS. 9 and 10, the lower bush 59 is also called as a sliding bearing, or an oilless bush. It has a semi-cylindrical shape, is made of bronze or the like, and includes a countersink 91. The countersink 91 penetrates the lower bush 59 near the center of it. A flat head bolt 51b, shown in FIG. 14, is inserted through it. The flat head bolt 51b fixes the lower bush 59 to the lower block 58Z.
As shown in FIGS. 11 and 12, the lower block 58Z is made of steel or the like, and includes the followings.                A female screw hole 86. It is bored near the center of the recess 81 toward a D direction. It engages with the flat head bolt 51b to fix the lower bush 59 to the lower block 58Z.        Positioning holes 85a and 85b. They are bored from the upper face of the lower block 58Z toward the D direction. The knock pins 55a and 55b are fitted into them to position the upper block 56Z referring to the lower block 58Z.        Female screw holes 83a to 83c. They are bored from the upper face of the lower block 58Z toward the D direction. They engage with the bolts 53a to 53c to fix the upper block 56Z to the lower block 58Z.        Positioning holes 84a and 84b. They penetrate the lower block 58Z in the U-D direction. Knock pins 54a, shown in FIG. 14, and 54b, not shown, are fitted through them. The knock pins 54a and 54b are fitted into positioning holes provided on the base 11 to position the lower block 58Z referring to the base 11.        Bolt holes 82a to 82c. They penetrate the lower block 58Z in the U-D direction. Bolts 52a to 52c, shown in FIG. 14, are inserted through them. The bolts 52a to 52c screw into and engage with female screw holes provided on the base 11 to fix the lower block 58Z to the base 11.        
As shown in FIGS. 13 and 14, the knock pins 54a and 54b position the lower block 58Z referring to the base 11, and the bolts 52a to 52c fix the lower block 58Z to the base 11. This enables to position the recess 81 referring to the base 11 with extreme accuracy.
Also, the knock pins 55a and 55b position the upper block 56Z referring to the lower block 58Z, and the bolts 53a to 53c fix the upper block 56Z to the lower block 58Z. This enables to position the recess 61Z referring to the recess 81 with extreme accuracy.
At the time of pivot movement, the shaft 41 of the pivoting body 14 slides with the upper bush 57 and the lower bush 59 located in the recesses 61Z and 81. Thus, the shaft hole portion formed by the recesses 61Z and 81 is required to have a perfect circular column shape with extreme accuracy. To realize the required accuracy, the bearing unit 15Z is produced, e.g., by the following procedure.
First, a block 26Z, shown in FIG. 15, with a rectangular parallelepiped shape, and a block 28Z, shown in FIG. 15, with a rectangular parallelepiped shape are provided. The upper block 56Z is formed by processing the block 26Z. The lower block 58Z is formed by processing the block 28Z.
Next, the two blocks 26Z and 28Z are processed to form the bolt holes 62a to 62c and 82a to 82c, the female screw holes 83a to 83c, and the positioning holes 64a, 64b, 84a, 84b, 85a and 85b. 
Then, as shown in FIG. 15, the block 26Z is mounted on the block 28Z. The knock pins 55a and 55b fix the positional relation between the blocks 26Z and 28Z. The bolts 53a to 53c fix the block 26Z to the block 28Z. In this manner, the two blocks 26Z and 28Z are unified in the same way as the bearing unit 15Z when in use, to form a workpiece block.
And, the unified workpiece block is processed to form a penetrating hole with a perfect circular column shape with extreme accuracy, so as to form the recesses 61Z and 81.
When in use, the recesses 61Z and 81, formed in this manner, are positioned and combined with high accuracy. This enables to reproduce the penetrating hole as the shaft hole portion having a perfect circular column shape with extreme accuracy.
It should be noted that the combination of the upper block 56Z and the lower block 58Z formed in this manner can not be changed. That is, combining a particular lower block 58Z with an upper block 56Z other than the particular one unified and processed with the particular lower block 58Z fails to make the shaft hole portion to have a perfect circular column shape with extreme accuracy.
Accordingly, signs are given to the upper block 56Z and the lower block 58Z. For example, matchmarks are stamped. The signs show that the two blocks have been unified and processed. This enables to correctly combine the upper block 56Z and the lower block 58Z.
JP 2007-283352 A discloses a similar bearing structure.